Counterbalance means for unequal reciprocating loads



.1. CHASTAIN July s, 1958 COUNTERBALANCE MEANS FOR UNEQUAL RECIPROCATING LOADS Filed Sept. 13, 1954 uDOkOh INVENTOR Joe 6/; as/ain ATTORNEY 4 UP STOKE I- United States Patent COUNTERBALAN CE MEANS FOR UNEQUAL RECIPROCATING LOADS Joe Chastain, Midland, Tex.

Application September 13, 1954, Serial No. 455,663

7 Claims. (CI. 74-41) This invention relates to counterbalance means for unequal reciprocating loads and more particularly to counterbalance means for reducing the peaktorque on drive shafts of power units moving such unequal reciprocating loads.

One object of the invention is to provide a new and improved counterbalance means for unequal reciprocating loads for reducing the peak torque on the drive shaft of the power unit moving such loads.

Another object of the invention is to provide a new and improved counterbalance means adapted for application to reciprocating movement pumps, and providing load equalizing means whereby the variations in the load on the motor driving the pump are minimized during each cycle of operation of the pump.

Still another object of the invention is to provide a new and improved pump, of the type described, having a counterbalance means which automatically varies in accordance with the reciprocating movement of the pull rods of the pump to minimize the variations in the load on the motor during operation of the pump.

A further object of the invention is to provide a new and improved pump, of the type described, having a counterbalance arm provided with a counterbalance weight which is moved in accordance with the movement of the lifting rods of the pump to minimize the variations in the load to which the driving motor is subjected during each cycle of operation of the pump.

Additional objects and advantages of the invention will be readily apparent from the reading of the following description of a device constructed in accordance with the invention, and referenceto the accompanying drawings thereof, wherein:

Figure 1 is a largely schematic side view of a pump showing the elements thereof in the positions they assume during the upstroke of the pump;

Figure 2 is a side view of the pump showing the elements thereof in the positions they assume during the down stroke of the pump;

Figure 3 is a perspective fragmentary view of the driving crank arm showing a roller mounted on its wrist pin and the manner in which it engages the counterbalance beam and,

Figure 4 is graphic illustration of the torques impressed on the drive shaft of the motor driving the pump.

"Referring now to the drawings, the numeral designates generally a pump which inclueds a piston 11 slidable in a conductor 12 whose open lower end communicates with a pool 13 of liquid which is to be lifted to the surface and expelled through the outlet 14. The piston is provided with a conventional by-pass valve or gasket (not shown), which permits flow of the liquid in the conductor past the piston during the downward stroke of the piston and which prevents flow of the liquid in the conductor past the piston during the up-stroke of the piston.

The piston is reciprocated bymeans of a string of lift rods 15 whose lower end is secured to the piston and whose under end is connected, as by the pin 16, to one end of a lever or pump jack 17, which is pivotally connected intermediate its ends, as by a pivot pin 18, to a fixed structure or base 19. The end of the pump jack remote from the lifting rods is pivotally connected by a pin 20 to the lower end of a pitman 21 whose upper end is pivotally connected to the outer end of a crank arm 23 by an elongated wrist pin 24.

The inner end of the crank arm is rigidly secured to a drive shaft 28 of a speed reducer 29 which is driven by a motor 31 connected by means of a chain or belt 32 with the pulley 33 of the speed reducer. The speed reducer is mounted on a suitable base or platform 34.

It will thus be seen that the pump jack 17, the pitman 21 and the crank arm 23 constitute a mechanical linkage between the drive shaft 28 and the lifting rods 15 of the pump, and that this linkage mechanism reciprocates the lifting rods during each revolution of the drive shaft of the speed reducer.

It will be also be apparent that the torque on the drive shaft caused by the weight of the lift rods, the piston and the column of fluid supported on the piston will change during each cycle of operation of the pump as diagrammatically and arbitrarily shown by the curve A in Figure 4. It will be noted that the peak torque load on the upstroke will have a large positive value because of the weight of the lift rods and of the fluid supported on the piston, while on the downstroke the weight of the lift rods and such fluid as remains above the piston acts to produce a large negative torque. The greater the weight of the lift rods and the column of fluid, the greater will be the peak torque on the driving shaft during the down and up strokes of the pump during each cycle of operation of the pump, and the greater are the loads imposed on the speed reducer and the motor.

In order to reduce these torque peaks, at counterbalance means 36 is provided which includes an elongate counterbalance arm 37 pivoted at one end by means of the pin 38 to the platform 34 and which rides on a roller 39 mounted on the wrist pin 24 of the crank arm 23. A counterbalance weight 40 is slidably mounted on the outer end of the counterbalance arm 37 and can be rigidly secured in any adjusted position by means of a lock' screw 41 threaded therethrough to engage the counterbalance arm.

It will now be seen that the torque or force applied to or imposed on the drive shaft 28 by the counterbalance means during each cycle of operation will vary in the manner defined by the curve B, since the load imposed on the wirst pin by thecounterbalance weight 40 varies as a function of the distances of the counterbalance weight 40 from the pivot pin 38 and of the wrist pin 24 from said pivot pin. The torque or force will, of course, be greatest when the crank arm and counterbalance arm are in the position shown in Figure 1, since the ratio of the distance of the wrist pin 24 from the pivot pin 38 to the distance of the weight 40 from the pivot pin 38 is greatest when the crank arm 37 is in this innermost position, with the wrist pin nearest the pivot pin 38. The torque or force imposed by the Weight 40 on the drive shaft will be smallest when the crank arm is in a position opposite that shown in Figure 1, since the ratio of the distance of the wrist pin from the pivot pin 38 to the distance of the Weight 40 from the pivot is smallest when the crank arm 37 is in this outermost position relative to the pivot pin.

As will be evident from an inspection of Figure 4, the torque on the drive shaft 28 represented by the curve B and caused by the counterbalance mechanism 36 is opposite to the torque on the drive shaft 28 represented by the curve A and caused by the weight of the pull rods, the piston and the column of fluid supported on the piston, so that the resultant torque on the drive shaft is the difference between these torques and is represented by the curve C.

It will now be apparent that the counterbalance mechanism 36 creates a torque on the drive shaft 28 which varies inversely as the torque created on the drive shaft by the normal load of the pump mechanism, and this will minimize the peak torque on the drive shaft 28 and load imposed on the motor 31. It will also be apparent that, due to this reduction of peak torques, the use of smaller motors and speed reducers is made possible, savings in power consumption are effected and efficiency of operation is improved.

If desired, and additional counterbalance weight 42 may be secured to the pump jack 17 to counterbalance at least partially the weight of the lift rods.

It will be apparent that the counterbalance weight 40 may be slid along the counterbalance arm 37 to any desired position thereon to adjust the effect of the counterbalance mechanism as desired for optimum operation. it will also be apparent that the weight 40 may be made integral with the counterbalance arm and of any other desired configuration than that shown.

The foregoing description of the invention is explanatory only, and changes in the details of the constructions illustrated may be made by those skilled in the art, within the scope of the appended claims, without departing from the spirit of the invention.

What i claim and desire to secure by Letters Patent is:

1. A device of the type described including: a drive shaft; a crank arm having one end rigidly secured to said drive shaft; means secured to the other end of said crank arm connecting said crank arm to a load; and a counterbalance mechanism for reducing the peak torques to which the drive shaft is subjected, comprising: a counterbalance arm pivoted at one end to a fixed structure, means movably connecting said counterbalance arms to said other end of said crank arm to move said counter baiance arm about said pivot as said drive shaft revolves, and a weight on said counterbalance arm spaced outwardly from the pivot beyond the connection between the crank arm and the counterbalance arm, said movable connection between said crank arm and said counterbalance arm moving circularly about said drive shaft as said drive shaft rotates, whereby said weight imposes a torque on said drive shaft which varies inversely with the torque imposed on said drive shaft by said load.

2. A pump including: lift means and a piston reciprocable therewith vertically; a drive shaft rotatable about a horizontal axis; a crank arm having one end rigidly secured to said drive shaft; a mechanical linkage connecting the opposite end of said crank arm to said lift for effecting reciprocal movement of said lift means upon rotation of said drive shaft; and a counterbalance mechanism comprising: a counterbalance arm pivotable at one end about a second horizontal axis, and means movably connecting said counterbalance arm to said other end of said crank arm whereby said counterbalance arm is pivoted about said second horizontal axis when said drive shaft revolves, said horizontal axis being parallel; said means movably connecting said crank arm to said counterbalance arm moving circularly downwardly about said drive shaft as said drive shaft rotates during movement of the crank arm lifting said lift means and circularly upwardly during movement of the crank arm lowerin. said lift means, whereby the counterbalance arm imposes a torque on said drive shaft which varies inversely with the torque imposed on said drive shaft by said lift means.

3. A pump including: a lift rod and piston reciprocable vertically; a drive shaft rotatable about a horizontal axis; a crank arm'having one end rigidly secured to said drive shaft; a mechanical linkage connecting the opposite end of said crank arm to said lift rod for effecting reciprocal movement of said lift rod upon rotation of said drive shaft; and a counterbalance mechanism comprising: a counterbalance arm pivotable at one end about a second horizontal axis, and means movably conmeeting said counterbalance arm to said other end of said crank arm whereby said counterbalance arm is pivoted about said second horizontal axis when said drive shaft revolves, said horizontal axis being parallel, and a weight on said counterbalance arm spaced out wardly from said pivot beyond said movable connection between the crank arm and said counterbalance arm, whereby said connection is between the weight and the pivot.

4. A pump including: a lift rod and piston reciprocable vertically; a drive shaft rotatable about a horizontal axis; a crank arm having one end rigidly secured to said drive shaft; a mechanical linkage connecting the opposite end of said crank arm to said lift rod for effecting reciprocal movement of said lift rod upon rotation of said drive shaft; and a counterbalance mechanism comprising: a counterbalance arm pivotable at one end about a second horizontal axis, a roller mounted on said other end of said crank arm, said roller having a third horizontal axis of rotation, said counterbalance arm resting on said roller, said horizontal axes being parallel, and a weight on said counterbalance arm spaced outwardly of said counterbalance arm beyond the point of engagement of the roller with counterbalance arm, whereby said roller engages the counterbalance arm between said weight and said pivot.

5. A device of the type described including: a drive shaft; a crank arm having one end rigidly secured to said drive shaft; means secured to the other end of said crank arm connecting said crank arm to a reciprocating unbalanced load; and a counterbalance mechanism for reducing the peak torques to which the drive shaft is subjected comprising: a counterbalance arm pivoted at one end to a fixed structure, means movably connecting said counterbalance arm to said other end of said crank arm to move said counterbalance arm about said pivot as said drive shaft revolves, a weight on said counterbalance arm spaced outwardly of said counterbalance arm beyond the connection between the crank and said counterbalance arm, said connection between said crank arm and said counterbalance arm moving circularly about said drive shaft as said drive shaft rotates, whereby said weight imposes a torque on said drive shaft which varies in accordance with the torque imposed on said drive shaft by said load, said means providing the movable connection between said counterbalance arm and said crank arm including roller means on said other end of said crank arm, said counterbalance arm resting on said roller means.

6. A device of the type described including: a reciprocably movable load; a drive shaft rotatable about a fixed axis; a crank arm having one end rigidly secured to said drive shaft; a mechanical linkage connecting the opposite end of said crank arm to said load for effecting reciprocal movement of said load upon rotation of said drive shaft; and a counterbalance mechanism comprising: a loaded counterbalance arm pivotable at one end about a second fixed axis, and means movably connecting said counterbalance arm to said other end of said crank arm whereby said counterbalance arm is pivoted about said second fixed axis when said drive shaft revolves, the point of connection between said counterbalance arm and said crank arm shifting toward and from said second axis whereby said counterbalance arm imposes a torque on said drive shaft varying inversely as the torque imposed by said reciprocably movable load.

7. A device of the type described including: a drive shaft; a crank arm having one end rigidly secured to said drive shaft; means secured to the other end of said crank arm connecting said crank arm to a load; and a counterbalance mechanism for reducing the peak torques to which the drive shaft is subjected, comprising: a counterbalance arm pivoted at one end to a fixed structure, means movably connecting said counterbalance arm to said other end of said crank arm to move said counterbalance arm about said pivot as said drive shaft revolves, and a weight on said counterbalance arm moving circularly about said drive shaft as said drive shaft revolves whereby said weight imposes a torque on said drive shaft which varies inversely with the torque imposed on said drive shaft by said load.

UNITED STATES PATENTS Rigby Sept. 5, Dayton July 15, Allen May 27, Casey Feb. 20, Slonneger Dec. 10, Porter Apr. 23, Tucker Nov. 8, 

